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9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
9. Blood, Lymph and Immunity
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9. Blood, Lymph and Immunity

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    • 1. Blood, Lymph and Immunity
    • 2. Learning Objectives <ul><li>List and describe the functions of blood. </li></ul><ul><li>Describe the composition of blood plasma and the characteristics of mature erythrocytes. </li></ul><ul><li>Describe the structure of the hemoglobin molecule. Explain the fate of hemoglobin following intravascular and extravascular hemolysis. </li></ul><ul><li>Give the origin of thrombocytes. Describe their characteristics and functions. </li></ul><ul><li>List the types of leukocytes and describe the functions of each. </li></ul><ul><li>Describe the formation of lymph fluid and its circulation through the lymphatic system. </li></ul><ul><li>List the functions of the lymphatic system. Describe the structure and function of the lymph nodes, spleen, thymus, tonsils, and GALT. </li></ul><ul><li>List the functions of the immune system. Differentiate between specific and nonspecific immune reactions; cell-mediated and humoral immunity. </li></ul><ul><li>List the components of cell-mediated immunity. Explain the role of each. </li></ul><ul><li>List and describe the classes of immunoglobulins. Differentiate between active and passive immunity. </li></ul>
    • 3. Functions of Blood <ul><li>Transportation </li></ul><ul><ul><li>Oxygen, nutrients ,waste products, hormones </li></ul></ul><ul><li>Regulation </li></ul><ul><ul><li>Body temperature, tissue fluid content, blood pH </li></ul></ul><ul><li>Defense System </li></ul><ul><ul><li>White blood cell phagocytosis, platelets, clotting factors </li></ul></ul>
    • 4. Composition of Blood <ul><li>Liquid portion: Plasma </li></ul><ul><li>Cellular portion: </li></ul><ul><ul><li>Red blood cells ( erythrocytes ) </li></ul></ul><ul><ul><li>White blood cells ( leukocytes ) </li></ul></ul><ul><ul><li>Platelets ( thrombocytes ) </li></ul></ul>
    • 5. Plasma <ul><li>45% to 78% of a blood sample volume, depending on the species of the animal and the size of its red blood cells </li></ul><ul><li>93% water </li></ul><ul><li>Substances dissolved or suspended in plasma </li></ul><ul><ul><li>Albumin, globulins, and fibrinogen </li></ul></ul><ul><ul><li>Oxygen, carbon dioxide, and nitrogen </li></ul></ul><ul><ul><li>Lipids, amino acids, metabolic wastes, and electrolytes </li></ul></ul>
    • 6. Cellular Components <ul><li>Erythrocytes - carry oxygen </li></ul><ul><li>Thrombocytes - help prevent leaks from damaged blood vessels </li></ul><ul><li>Leukocytes </li></ul><ul><ul><li>Granulocytic or agranulocytic </li></ul></ul><ul><ul><li>Multiple functions </li></ul></ul>
    • 7. Hematopoiesis <ul><li>Production of all blood cells </li></ul><ul><li>Occurs primarily in red bone marrow </li></ul><ul><li>Fetal hematopoiesis occurs in the liver and spleen </li></ul><ul><li>Neonatal hematopoiesis occurs in red bone marrow </li></ul>
    • 8. Hematopoiesis <ul><li>Older animals </li></ul><ul><ul><li>Some red bone marrow is converted to inactive, yellow bone marrow </li></ul></ul><ul><ul><ul><li>Composed of fat cells that have replaced some of the active red marrow </li></ul></ul></ul><ul><ul><li>In a mature animal most red bone marrow is found at the ends of long bones and in flat bones </li></ul></ul><ul><ul><li>Liver and spleen have a limited capacity to participate in hematopoiesis </li></ul></ul>
    • 9. Hematopoiesis <ul><li>Hematopoietic stem cell </li></ul><ul><ul><li>Pluripotent </li></ul></ul><ul><ul><li>Can develop into any one of the blood cells </li></ul></ul><ul><ul><ul><li>Depends on chemical or physiological stimuli </li></ul></ul></ul><ul><ul><ul><li>Involves numerous cell divisions </li></ul></ul></ul>
    • 10. Erythropoiesis <ul><li>Production of red blood cells </li></ul><ul><ul><ul><ul><li>Erythropoietin: hormone released from cells in kidney in response to hypoxia </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Triggers stem cell to divide and differentiate </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><li>Multiple maturation steps </li></ul></ul></ul></ul>
    • 11. Red Blood Cells <ul><li>Characteristics </li></ul><ul><li>~65% water and 35% solids </li></ul><ul><ul><li>Primary solid - hemoglobin </li></ul></ul><ul><li>Round, anuclear biconcave disks (most mammals) </li></ul><ul><ul><li>Variable sizes </li></ul></ul><ul><ul><li>Uses plasma glucose for energy </li></ul></ul>
    • 12. Hemoglobin <ul><li>Composed of heme and globin </li></ul><ul><li>Heme - pigment portion; produced in the mitochondria; contains iron atoms (Fe ++ ) </li></ul><ul><ul><li>Every heme group can carry one molecule of oxygen. </li></ul></ul><ul><ul><li>Four heme groups attach to each globin molecule. </li></ul></ul><ul><li>Globin - protein portion; produced by ribosomes </li></ul>
    • 13. Normal Hemoglobin Types <ul><li>Embryonic hemoglobin (HbE) - found in developing fetuses. </li></ul><ul><li>Fetal hemoglobin (HbF) - found in fetal blood during mid- to late gestation and up to a couple months after birth </li></ul><ul><li>Adult hemoglobin - found in the red blood cells of all animals beginning a couple of weeks to a couple of months after birth </li></ul>
    • 14. Hemoglobin <ul><li>Oxyhemoglobin - hemoglobin that is carrying oxygen. </li></ul><ul><ul><li>One oxygen molecule is associated with each iron (Fe ++ ) molecule </li></ul></ul><ul><li>Deoxyhemoglobin - hemoglobin that has released its oxygen </li></ul>
    • 15. Carbon Dioxide Transport <ul><li>CO 2 diffuses into red blood cells and is transformed into carbonic acid </li></ul><ul><li>Ionizes into hydrogen ions and bicarbonate ions </li></ul><ul><ul><li>H 2 O + CO 2 = H 2 CO 3 = H + + HCO3 – </li></ul></ul><ul><ul><li>Deoxyhemoglobin accepts the hydrogen ion. </li></ul></ul><ul><ul><li>Bicarbonate diffuses back into the plasma. </li></ul></ul>
    • 16. Red Blood Cell Life Span <ul><li>Varies with the species </li></ul><ul><ul><li>Dogs ~ 110 days </li></ul></ul><ul><ul><li>Cats ~ 68 days </li></ul></ul><ul><ul><li>Horse and sheep ~ 150 days </li></ul></ul><ul><ul><li>Cow ~ 160 days </li></ul></ul><ul><ul><li>Mice ~ 20-30 days </li></ul></ul><ul><li>Senescence - process of aging </li></ul>
    • 17. Red Blood Cell Senescence <ul><li>Enzyme activity decreases </li></ul><ul><li>Cell loses its deformability </li></ul><ul><ul><li>Becomes rounder; volume decreases </li></ul></ul><ul><li>Extravascular hemolysis </li></ul><ul><ul><li>Macrophages (especially in the spleen) remove senescent RBCs from circulation </li></ul></ul><ul><ul><li>RBCs broken down into components that can be recycled in the body or eliminated as waste material </li></ul></ul>
    • 18. Red Blood Cell Senescence <ul><li>Extravascular hemolysis </li></ul><ul><li>RBC membrane is destroyed </li></ul><ul><li>Iron is transported to the red bone marrow </li></ul><ul><li>Amino acids from globin molecules are transported to the liver for re-use </li></ul>
    • 19. Red Blood Cell Senescence <ul><li>Heme is converted to bilirubin, bound to albumin, and transported to liver (unconjugated bilirubin) </li></ul><ul><li>Bilirubin is conjugated to glucuronic acid. </li></ul><ul><li>Conjugated bilirubin excreted as a bile pigment into intestines </li></ul><ul><li>Converted into urobilinogen by bacteria </li></ul><ul><ul><li>Some is reabsorbed and eliminated in urine as urobilin; some is converted to stercobilinogen and excreted in stool as stercobilin. </li></ul></ul>
    • 20. Red Blood Cell Senescence <ul><li>Intravascular hemolysis </li></ul><ul><li>RBCs in circulation subjected to stresses </li></ul><ul><ul><li>Can result in RBC fragmentation and/or destruction </li></ul></ul><ul><ul><li>Hemoglobin released directly into the blood </li></ul></ul>
    • 21. Red Blood Cell Senescence <ul><li>Intravascular hemolysis </li></ul><ul><li>Unconjugated hemoglobin attached to haptoglobin </li></ul><ul><ul><li>Transported to macrophages in the liver </li></ul></ul><ul><ul><li>Processed as with extravascular hemolysis </li></ul></ul><ul><li>Excess unconjugated hemoglobin in the plasma (hemoglobinemia) is eliminated in urine (hemoglobinuria) </li></ul>
    • 22. Anemia <ul><li>Results in decreased O 2 carrying capacity of the blood </li></ul><ul><li>Caused by: </li></ul><ul><ul><li>Low number of circulating mature red blood cells (blood loss, increased RBC destruction, decreased RBC production) </li></ul></ul><ul><ul><li>Insufficient hemoglobin production (e.g., iron deficiency) </li></ul></ul>
    • 23. Polycythemia <ul><li>Increase in number of RBCs </li></ul><ul><li>Three types: </li></ul><ul><ul><li>Relative polycythemia - hemoconcentration due to fluid loss (e.g., vomiting, diarrhea) </li></ul></ul><ul><ul><li>Compensatory polycythemia - result of hypoxia (e.g., high altitudes, congestive heart failure) </li></ul></ul><ul><ul><li>Polycythemia rubra vera - rare bone marrow disorder; cause unknown </li></ul></ul>
    • 24. Platelets (Thrombocytes) <ul><li>Cytoplasmic fragments of bone marrow megakaryocytes </li></ul><ul><li>Thrombopoiesis - production of platelets </li></ul><ul><li>Megakaryocyte undergoes incomplete mitosis during maturation </li></ul><ul><ul><li>Nuclei divide, cytoplasm doesn’t </li></ul></ul><ul><ul><li>Results in multinucleated cell with abundant cytoplasm </li></ul></ul>
    • 25. Platelet Characteristics <ul><li>Circulating platelets are round with numerous small, purple granules </li></ul><ul><li>Granules contain some of the clotting factors and calcium </li></ul><ul><li>Platelets remain in peripheral blood until they are removed by tissue macrophages because of old age or damage. </li></ul>
    • 26. Platelet Functions <ul><li>Maintain vascular integrity </li></ul><ul><ul><li>Release endothelial growth factor into blood vessel endothelial cells </li></ul></ul><ul><li>Formation of platelet plug </li></ul><ul><ul><li>Attracted to exposed connective tissue of damaged blood vessel </li></ul></ul><ul><ul><li>Adhere to exposed connective tissue and each other </li></ul></ul><ul><li>Stabilize the hemostatic plug </li></ul><ul><ul><li>Fibrin strands form a netlike mesh around and through the platelets. </li></ul></ul>
    • 27. White Blood Cells (Leukocytes) <ul><li>Classifications: </li></ul><ul><ul><li>Functions </li></ul></ul><ul><ul><li>Presence or absence of granules </li></ul></ul><ul><ul><li>Nuclear shape </li></ul></ul>
    • 28. Table 9-2. White Blood Cells NAME CYTOPLASMIC GRANULES NUCLEAR SHAPE FUNCTION SITE OF ACTION Neutrophil Don’t stain (usually invisible) Polymorphonuclear Phagocytosis Body tissues Eosinophil Stain red Polymorphonuclear Allergic reactions, anaphylaxis, phagocytosis Body tissues Basophil Stain blue Polymorphonuclear Initiation of immune and allergic reactions Body tissues Monocyte (Macrophage) None Pleomorphic Phagocytosis and process antigens Body tissues or blood B cell None Mononuclear Antibody production and humoral immunity Lymphoid tissue T cell None Mononuclear Cytokine production and cell-mediated immunity Lymphoid tissue and other body tissues
    • 29. Leukopoiesis <ul><li>Occurs in red bone marrow </li></ul><ul><ul><li>Some lymphocytes develop further outside bone marrow </li></ul></ul><ul><li>Same pluripotent stem cell that produces red blood cells and megakaryocytes </li></ul><ul><li>Each type of WBC has its own stimulus for production </li></ul>
    • 30. Granulopoiesis <ul><li>Production of the neutrophils, eosinophils, and basophils </li></ul><ul><li>Initially there are no cytoplasmic granules, then non-specific granules are formed </li></ul><ul><li>Specific granules produced during maturation </li></ul><ul><ul><li>Granules contain different substances depending on the cell’s function </li></ul></ul><ul><ul><li>Example: neutrophil granules contain lysosomal enzymes used in phagocytosis </li></ul></ul>
    • 31. Neutrophil Characteristics <ul><li>Polymorphonuclear cells; segs </li></ul><ul><li>Most numerous WBC in circulation in the dog, horse, and cat </li></ul><ul><li>Granules don’t stain with either the blue alkaline stain or the red acid stain (neutral staining). </li></ul>
    • 32. Neutrophils <ul><li>Mature neutrophils in circulation have two to five nuclear segments joined by a strand of chromatin. </li></ul><ul><li>Immature neutrophils have a horseshoe nucleus without any segmentation (band neutrophil). </li></ul><ul><li>Neutrophil function: phagocytosis </li></ul><ul><ul><li>Granules contain lysosomes capable of destroying bacteria and viruses that have been engulfed </li></ul></ul>
    • 33. Neutrophil Characteristics <ul><li>In peripheral circulation for about 10 hours </li></ul><ul><li>Diapedesis - process used by neutrophils to go from circulation into tissue spaces </li></ul><ul><li>Chemotaxis - process that attracts neutrophils to inflammatory chemicals at a site of infection </li></ul>
    • 34. Neutrophil Action <ul><li>Outer membrane flows around the microorganisms and encases them within a membrane-bound phagocytic vacuole </li></ul><ul><li>Cytoplasmic granules move to the edge of the vacuole and fuse with its membrane </li></ul><ul><ul><li>Secrete lysosomes into the vacuole </li></ul></ul>
    • 35. Neutrophils <ul><li>Hydrogen peroxide - produced by neutrophils during oxygen metabolism </li></ul><ul><ul><li>Bactericidal </li></ul></ul><ul><li>Myeloperoxidase - released from neutrophil granules </li></ul><ul><ul><li>Enhances the bactericidal action of hydrogen peroxide </li></ul></ul><ul><ul><li>Capable of destroying the cell walls of microorganisms </li></ul></ul>
    • 36. Neutrophil Count <ul><li>Relatively stable range in peripheral blood </li></ul><ul><li>Controlled by </li></ul><ul><ul><li>Release of mature neutrophils from the storage pool in bone marrow into the peripheral blood </li></ul></ul><ul><ul><li>Rate of escape from peripheral blood into tissue </li></ul></ul><ul><ul><li>Entrance of increased numbers of pluripotent stem cells into the neutrophil production line </li></ul></ul>
    • 37. Intravascular Pools of Neutrophils <ul><li>Circulating pool - within lumen of blood vessels </li></ul><ul><li>Marginal pool - line the walls of small blood vessels mainly in the spleen, lungs, and abdominal organs </li></ul>
    • 38. Eosinophil Characteristics <ul><li>Red granules in the cytoplasm of mature cells </li></ul><ul><li>0-5% of the total white blood cell count </li></ul><ul><li>Produced in bone marrow from the same pluripotent stem cell that gives rise to all other blood cells </li></ul><ul><li>Segmented nucleus - usually two lobes </li></ul>
    • 39. Eosinophil Characteristics <ul><li>Granule shape varies </li></ul><ul><ul><li>Dogs: round granules of varying sizes; pale staining </li></ul></ul><ul><ul><li>Cats: numerous small, rod-shaped granules </li></ul></ul><ul><ul><li>Horses: very large, round or oval-shaped granules; stain intensely </li></ul></ul><ul><ul><li>Cattle, sheep, and pigs: round, small granules; stain pink to red </li></ul></ul>
    • 40. Eosinophil Pools <ul><li>Bone marrow reserve </li></ul><ul><li>Circulating pool </li></ul><ul><li>Marginal pool </li></ul><ul><li>Migrate into tissue within a few hours of release from bone marrow </li></ul>
    • 41. Eosinophil Functions <ul><li>Anti-inflammatory: granules contain anti-inflammatory substances </li></ul><ul><li>Immunity: can ingest substances associated with the humoral immune response </li></ul><ul><li>Phagocytosis: minimal phagocytotic and bactericidal functions; usually large organisms such as protozoa and some parasitic worms </li></ul>
    • 42. Eosinophilia <ul><li>Causes: </li></ul><ul><ul><li>Increased release of mature eosinophils </li></ul></ul><ul><ul><li>Migration of eosinophils from marginal pool to circulating pool </li></ul></ul><ul><ul><li>Increased production </li></ul></ul><ul><ul><li>Longer time in peripheral blood before entering tissue </li></ul></ul><ul><li>Accompanying leukocytosis may not occur </li></ul><ul><li>Eosinopenia (decreased numbers) - difficult to detect because numbers are normally low. </li></ul>
    • 43. Basophil Characteristics <ul><li>Blue granules in the cytoplasm of mature cells </li></ul><ul><ul><li>Not always visible on stained smear </li></ul></ul><ul><ul><li>May completely fill the cytoplasm </li></ul></ul><ul><li>Least often seen WBC in circulation </li></ul><ul><li>Dog has fewer granules than the other common domestic species </li></ul><ul><li>Nucleus usually has 2 to 3 lobes </li></ul>
    • 44. Basophils and Tissue Mast Cells <ul><li>Theories regarding the relationship between mast cells and basophils: </li></ul><ul><ul><li>Two different cell types with similar characteristics; produced in different areas and don’t give rise to one another </li></ul></ul><ul><ul><li>Mast cells are tissue basophils </li></ul></ul>
    • 45. Basophil Functions <ul><li>Granules contain histamine and heparin </li></ul><ul><ul><li>Histamine helps initiate inflammation and acute allergic reactions. </li></ul></ul><ul><ul><li>Heparin acts as a localized anticoagulant to keep blood flowing to an injured or damaged area. </li></ul></ul><ul><li>Eosinophils are attracted to site of an allergic reaction by chemotactic factor released from basophil granules </li></ul>
    • 46. Basophilia and Basopenia <ul><li>Basophilia - can be associated with an allergic or hypersensitivity reaction in tissue </li></ul><ul><ul><li>May occur in conjunction with eosinophilia </li></ul></ul><ul><li>Basopenia - difficult to evaluate because numbers are normally low </li></ul>
    • 47. Monocyte Characteristics <ul><li>5-6% of all circulating WBCs in common domestic species </li></ul><ul><li>Largest white blood cells in circulation </li></ul><ul><li>Abundant cytoplasm stains gray-blue </li></ul><ul><ul><li>May contain vacuoles of varying sizes </li></ul></ul><ul><ul><li>Cytoplasm may take on a fine granular appearance </li></ul></ul><ul><li>Nucleus - pleomorphic, non-segmented </li></ul>
    • 48. Monocyte Functions <ul><li>Important phagocytic cells </li></ul><ul><li>Known as tissue macrophages when in tissue spaces </li></ul><ul><li>Found in organs that remove or contain foreign invaders, damaged/old blood cells, and cellular debris (liver, spleen, lung, lymph nodes) </li></ul><ul><li>Tissue macrophages and monocytes are known as the mononuclear phagocyte system (MPS). </li></ul>
    • 49. Monocyte Functions <ul><li>Remove cellular debris that remains after an inflammation and/or infection clears up </li></ul><ul><li>Process certain antigens, making them more antigenic </li></ul><ul><ul><li>Present antigens to lymphocytes as part of immune response </li></ul></ul><ul><li>Ingest foreign substances </li></ul>
    • 50. Monocyte Functions <ul><li>Follow neutrophils into tissue (chemotaxis) in response to tissue damage caused by trauma or invading microorganisms </li></ul><ul><li>Remain at site of damage longer than neutrophils </li></ul><ul><li>Function in circulating blood to phagocytize damaged blood cells or microorganisms found in the blood (septicemia) </li></ul>
    • 51. Monocytosis and Monocytopenia <ul><li>Monocytosis </li></ul><ul><ul><li>Increased number of monocytes in peripheral blood </li></ul></ul><ul><ul><li>Often associated with a chronic inflammatory condition </li></ul></ul><ul><li>Monocytopenia </li></ul><ul><ul><li>Decreased number of monocytes in peripheral blood </li></ul></ul><ul><ul><li>Difficult to evaluate because numbers are normally low </li></ul></ul>
    • 52. Lymphocytes <ul><li>Primary circulating WBC in ruminants and pigs </li></ul><ul><li>No phagocytic capabilities </li></ul><ul><li>Most reside in lymphoid tissues and circulate between these tissues and blood </li></ul><ul><li>Thought to arise from the same pluripotent stem cell in the bone marrow as other blood cells </li></ul><ul><ul><li>Some lymphocytes leave the bone marrow and mature in other central lymphoid organs </li></ul></ul>
    • 53. Types of Lymphocytes <ul><li>Every lymphocyte has surface markers that differentiate subsets of each type of lymphocyte. </li></ul><ul><ul><li>Markers are not visible under light microscopy. </li></ul></ul><ul><li>Three type of Lymphocytes: </li></ul><ul><ul><li>T-lymphocytes (T cells) </li></ul></ul><ul><ul><li>B-lymphocytes (B cells) </li></ul></ul><ul><ul><li>Natural Killer (NK) Cells </li></ul></ul>
    • 54. T-Lymphocytes <ul><li>Processed in the thymus before going to peripheral lymphoid tissue </li></ul><ul><ul><li>Pre-T cells in the thymus are thymocytes </li></ul></ul><ul><li>Responsible for cell-mediated immunity and for activating B cells </li></ul><ul><li>Most of the lymphocytes in peripheral blood are T cells. </li></ul>
    • 55. B-Lymphocytes <ul><li>“Bursa equivalent” - refers to bone marrow and other lymphoid tissue thought to be the equivalent of a bird organ called the bursa of Fabricius </li></ul><ul><li>Inactive B cells travel through lymph nodes, the spleen, and other lymphoid structures </li></ul><ul><ul><li>Rarely circulate in peripheral blood. </li></ul></ul>
    • 56. B-Lymphocytes <ul><li>Responsible for antibody production </li></ul><ul><li>Each B cell produces only one specific antibody type against one specific antigen (foreign protein). </li></ul><ul><li>Surface receptors are shaped to fit only one antigen shape (epitope). </li></ul>
    • 57. B-Lymphocytes and Plasma Cells <ul><li>Humoral immunity: B cells recognize an antigen and transform into plasma cells </li></ul><ul><ul><li>Activated B cells multiply by mitosis (blastic transformation) to become plasma cells. </li></ul></ul><ul><ul><li>Plasma cells produce, store, and release antibodies (immunoglobins). </li></ul></ul>
    • 58. Natural Killer (NK) Cells <ul><li>NK cells don’t have to be activated by a specific antigen. </li></ul><ul><li>Have the ability to kill some types of tumor cells and cells infected with various viruses </li></ul><ul><li>Must come in direct contact with these cells before they can destroy them </li></ul>
    • 59. Lymphocyte Characteristics <ul><li>Circulating lymphocytes are classified as either large or small lymphocytes. </li></ul><ul><li>No cytoplasmic granules </li></ul><ul><li>Nucleus - round or oval, non-segmented </li></ul><ul><li>Large lymphocytes - abundant sky-blue cytoplasm </li></ul><ul><li>Small lymphocytes -scant amount of cytoplasm </li></ul>
    • 60. Memory Cells <ul><li>Both T cells and B cells can become memory cells. </li></ul><ul><li>Clones of an original lymphocyte </li></ul><ul><li>Reside in lymphoid tissue until second exposure to the same antigen encountered previously </li></ul><ul><li>Quicker and mounts a greater response than the initial immune response </li></ul>
    • 61. Lymphocytosis <ul><li>Lymphocytosis - increased number of lymphocytes in peripheral blood </li></ul><ul><ul><li>Can result from leukemia, chronic infection, epinephrine release </li></ul></ul><ul><ul><li>Can be significant enough to cause a leukocytosis </li></ul></ul>
    • 62. Lymphopenia <ul><li>Lymphopenia - decreased number of lymphocytes in peripheral blood </li></ul><ul><ul><li>Can result from decreased production, corticosteroids, immune deficiency diseases, acute viral diseases </li></ul></ul><ul><ul><li>Can result in a leukocytopenia </li></ul></ul>
    • 63. Lymphatic system <ul><li>Series of vessels/ducts </li></ul><ul><li>Carry excess interstitial tissue fluid to blood vessels near the heart where fluid is put back into the bloodstream </li></ul><ul><li>Also includes lymph tissue scattered throughout the body (lymph nodes, spleen, thymus, tonsils and gut associated lymph tissue [GALT]) </li></ul>
    • 64. Lymph <ul><li>Consists of: </li></ul><ul><ul><li>Blood cells - mostly lymphocytes </li></ul></ul><ul><ul><li>Nutrients (proteins, fats, etc.) </li></ul></ul><ul><ul><li>Hormones </li></ul></ul><ul><li>Some T cells circulate from blood to interstitial fluid to lymph and back to blood. </li></ul><ul><li>B cells are found primarily in lymph tissues and rarely recirculate. </li></ul>
    • 65. Lymph Formation <ul><li>Excess interstitial tissue picked up by small lymph capillaries that start blindly in the interstitial spaces of soft tissue </li></ul><ul><li>Fluid enters/leaves tissues spaces due to blood pressure and osmotic pressure </li></ul>
    • 66. Lymph Circulation <ul><li>Lymph capillaries join together to form larger and larger lymph vessels. </li></ul><ul><li>Many contain one-way valves that prevent lymph from flowing backwards. </li></ul><ul><li>Body movements propel lymph toward the heart. </li></ul><ul><li>Lymph vessels eventually join to form the thoracic duct that empties lymph into the vena cava just before it enters the heart. </li></ul>
    • 67. Lymph Circulation <ul><li>Lymph vessels pass through at least one lymph node and pick up lymphocytes. </li></ul><ul><li>Any microorganisms in the lymph are removed by macrophages found in the lymph nodes. </li></ul>
    • 68. Lymph Characteristics <ul><li>Transparent or translucent liquid containing varying numbers of cells, primarily lymphocytes </li></ul><ul><li>More water, sugar, and electrolytes than plasma </li></ul><ul><li>Fewer of the larger proteins found in plasma </li></ul><ul><li>Chyle - Lymph from the digestive system </li></ul><ul><ul><li>Chylomicrons cause lymph to appear white or pale yellow and cloudy. </li></ul></ul>
    • 69. Lymphatic System Functions <ul><li>Removal of excess tissue fluid </li></ul><ul><li>Waste material transport </li></ul><ul><ul><li>Interstitial fluid contains some of the waste materials from the tissue cells </li></ul></ul><ul><li>Filtration of lymph </li></ul><ul><ul><li>Removal of microorganisms, cellular debris, and other foreign matter </li></ul></ul><ul><li>Protein transport </li></ul>
    • 70. Lymph nodes <ul><li>Small kidney-bean-shaped structures located at various points along the lymph vessels </li></ul><ul><li>Connective tissue capsule sends branches (trabeculae) into the body of the lymph node </li></ul><ul><li>Afferent lymph vessels empty fluid just beneath the capsule. </li></ul><ul><li>Efferent vessels exit the lymph node in the indented hilus area. </li></ul>
    • 71. Lymph nodes <ul><li>Cortex - location of resident lymphocytes </li></ul><ul><ul><li>Lymph nodules: clusters of lymphocytes around periphery of the node </li></ul></ul><ul><li>Medulla - contains tissue macrophages embedded in a coarse fibrous mesh </li></ul>
    • 72. Spleen <ul><li>Tongue-shaped organ located on the left side of the abdomen </li></ul><ul><ul><li>Near the stomach in simple-stomached animals </li></ul></ul><ul><ul><li>Near the rumen in ruminants </li></ul></ul><ul><li>Largest lymphoid organ in the body </li></ul>
    • 73. Spleen <ul><li>Covered with a fibrous connective tissue capsule and smooth muscle </li></ul><ul><ul><li>Capsule sends branches (trabeculae) into the soft tissue of the spleen </li></ul></ul><ul><ul><li>Trabeculae contain blood vessels, nerves, lymph vessels, and smooth muscle cells. </li></ul></ul><ul><ul><li>Trabeculae are very muscular in carnivores. </li></ul></ul><ul><ul><li>When the smooth muscle cells contract, they squeeze blood out of the spleen and back into circulation. </li></ul></ul>
    • 74. Spleen <ul><li>Interior of the spleen is divided into white pulp and red pulp </li></ul><ul><li>White pulp: localized areas of lymphoid tissue </li></ul><ul><li>Red pulp: blood vessels, tissue macrophages, and blood sinuses (storage) </li></ul>
    • 75. Spleen Functions <ul><li>Blood storage in the red pulp </li></ul><ul><li>Removal of foreign material from circulation by the tissue macrophages in the red pulp </li></ul><ul><li>Removal of dead, dying and abnormal red blood cells by the tissue macrophages in the red pulp </li></ul><ul><li>Lymphocyte cloning in the white pulp during an immune response </li></ul>
    • 76. Thymus <ul><li>Lymphoid organ located in the caudal neck and cranial thoracic region on either side of the trachea. </li></ul><ul><li>Most prominent in young animals </li></ul><ul><li>Processes thymocyctes and T-cells </li></ul>
    • 77. Tonsils <ul><li>Nodules of peripheral lymphoid tissue </li></ul><ul><li>Not covered with a capsule </li></ul><ul><li>Found close to mucosal surfaces all over the body </li></ul><ul><ul><li>Pharynx, larynx, intestine, prepuce, and vagina </li></ul></ul><ul><li>Tonsils in pharyngeal region prevent spread of infection into the respiratory or digestive systems </li></ul><ul><li>Located at the beginning of the lymph drainage system, not along the lymph vessels like lymph nodes </li></ul>
    • 78. Gut Associated Lymph Tissue (GALT) <ul><li>Lymphoid tissue found in the intestinal mucosa and submucosa </li></ul><ul><li>Largest lymphoid organ in the body </li></ul><ul><li>GALT is classified as both central and peripheral lymphoid tissue. </li></ul>
    • 79. The Immune System <ul><li>Actions: </li></ul><ul><li>Phagocytosis and destruction of foreign cells </li></ul><ul><li>Lysis of foreign cell membranes </li></ul><ul><li>Inactivation of pathogenic organisms or chemical substances </li></ul><ul><li>Precipitation or agglutination of cells or molecules </li></ul>
    • 80. Nonspecific Immunity <ul><li>Mechanical barriers - skin and mucous membranes </li></ul><ul><li>Chemical barriers (e.g., hydrochloric acid in the gastric mucosa) </li></ul><ul><li>Inflammatory response - tissue damage provokes release of chemical mediators (e.g., histamine) and other chemotactic factors </li></ul><ul><li>Phagocytosis by neutrophils, monocytes and tissue macrophages </li></ul>
    • 81. Nonspecific Immunity <ul><li>Natural Killer cells - come in direct contact with tumor cells and tissue cells that have been invaded by viruses and destroy them </li></ul><ul><li>Interferon – protein produced by a cell after it has been infected by a virus; inhibits further development and spread of the virus </li></ul>
    • 82. Nonspecific Immunity <ul><li>Complement - group of enzymes in plasma that can be activated by the attachment of an antibody to an antigen </li></ul><ul><li>Complement fixation - cascade of reactions that results in antigen lysis </li></ul>
    • 83. Specific Immunity <ul><li>B cells that produce antibodies or direct other cells to attack the antigen </li></ul><ul><li>T cells that attack more directly </li></ul><ul><li>Response is initiated as a reaction to the epitope on the invading cell’s wall </li></ul><ul><li>Lymphocytes primarily involved but may depend on the actions of other cells for activation </li></ul>
    • 84. Table 9-3. Humoral Immune Response versus Cell Mediated Immune Response Humoral Immune Response Cell-Mediated Immune Response Cell type involved B cell that transforms into a plasma cell after antigenic stimulation T lymphocyte that transforms into cytotoxic T cell, helper T cell or supressor T cell after antigenic stimulation Substance produced Immunoglobulins (antibodies) Lymphokines Cellular mobility B cells and plasma cells stay in the lymphoid tissue. Antibodies are released into plasma. T cells can enter circulation and travel to the site where an antigen entered the body Memory cells produced? Yes Yes
    • 85. Types of Immunoglobulins (Ig) <ul><li>IgG - first Ig made during first exposure to an antigen </li></ul><ul><li>IgM - made when animal exposed to an antigen for a long time or when exposed to the antigen for the second time </li></ul><ul><li>IgA - can leave blood and enter tissue fluids; plays a role in protecting mucosal surfaces (e.g., intestinal tract and lungs) </li></ul><ul><li>IgE - associated with an allergic response </li></ul><ul><li>IgD - function is unknown </li></ul>
    • 86. Passive Immunity <ul><li>Animal receives preformed antibodies </li></ul><ul><ul><li>Antibodies produced by a mother that are passed to a fetus transplacentally </li></ul></ul><ul><ul><li>Ingestion of colostrum ( antibody-rich first milk produced) </li></ul></ul><ul><ul><li>Antibodies produced by another animal and given to a sick animal (e.g., administration of tetanus antitoxin) </li></ul></ul><ul><li>No memory cells produced </li></ul>
    • 87. Active Immunity <ul><li>Exposure to antigen that triggers animal’s own immune response </li></ul><ul><li>Memory T- or B cells are produced </li></ul><ul><li>Immunization: activate animal’s own immune systems </li></ul><ul><ul><li>Vaccines contain epitope of the antigens </li></ul></ul><ul><ul><li>Killed or live-but-weakened (attenuated) antigens </li></ul></ul>

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